1. Field of the Invention
The present invention relates to a mass spectrometer and a method of mass spectrometry. The preferred embodiment relates to 3D quadrupole ion traps (xe2x80x9cQITxe2x80x9d) and Time of Flight (xe2x80x9cTOFxe2x80x9d) mass analysers.
2. Discussion of the Prior Art
Known 3D (Paul) quadrupole ion trap mass spectrometers comprise a doughnut shaped central ring electrode and two end-cap electrodes. Such known 3D (Paul) quadrupole ion trap mass spectrometers typically have a relatively low resolution and a relatively low mass measurement accuracy when scanning the complete mass range compared with other types of mass spectrometers such as magnetic sector and Time of Flight mass spectrometers. 3D quadrupole ion traps do however exhibit a relatively high sensitivity in both MS and MS/MS modes of operation. One particular problem with 3D quadrupole ion traps is that they suffer from having a relatively limited mass range and exhibit a low mass to charge ratio cut-off limit below which ions cannot be stored within the quadrupole ion trap. In a MS/MS mode of operation only about a 3:1 ratio of parent mass to fragment mass can be stored and recorded.
Orthogonal acceleration Time of Flight mass spectrometers have relatively higher resolving powers and higher mass measurement accuracy for both MS and MS/MS modes. Typically, orthogonal acceleration Time of Flight mass spectrometers are coupled to ion sources which provide a continuous beam of ions. Segments of this continuous ion beam are then orthogonally extracted for subsequent mass analysis. However, about 75% of the ions are not extracted for mass analysis and are thus lost.
It is therefore desired to address the mass range limitation inherent with conventional quadrupole ion traps and to increase the duty cycle of an orthogonal acceleration Time of Flight mass analyser when performing MS and MS/MS experiments.
According to the present invention there is provided a mass spectrometer comprising:
a first ion trap and a second ion trap wherein the first ion trap is arranged to have, in use, a first low mass cut-off and the second ion trap is arranged to have, in use, a second low mass cut-off, the second low mass cut-off being lower than the first low mass cut-off so that at least some ions having mass to charge ratios lower than the first low mass cut-off which are not trapped in the first ion trap are trapped in the second ion trap.
Advantageously, the combination of two or more ion traps in series having different low mass cut-offs increases the overall ion trapping volume or capacity and hence the dynamic range of the ion trapping system.
A mass spectrometer according to the preferred embodiment is capable of performing both MS and MS/MS modes of operation and comprises an ion source, a series of coupled quadrupole ion traps and an orthogonal acceleration Time of Flight mass analyser. The combination of multiple quadrupole ion traps and the orthogonal acceleration Time of Flight mass analyser provides a mass spectrometer with an increased mass range (especially in MS/MS), increased sensitivity, increased mass measurement accuracy and increased mass resolution compared with other known arrangements.
According to a less preferred embodiment fragment ions may be generated externally to the first ion trap by surface induced disassociation (SID), collision induced disassociation (CID) or post source decay (PSD) and then transferred to the first ion trap.
According to the preferred embodiment collisional cooling with a bath gas may be employed in one or more of the ion traps and/or in the transfer region(s) between the ion traps. Collisional cooling advantageously reduces both the kinetic energy of the ions and the spread of kinetic energies of the ions. Collisional cooling also has the effect of improving the trapping efficiency within the ion trap whilst preparing the ions for subsequent mass analysis in a Time of Flight mass analyser, preferably an orthogonal acceleration Time of Flight mass analyser, which may optionally include a reflectron.
The first ion trap preferably comprises a quadrupole ion trap. According to the one embodiment the first ion trap comprises a 3D (Paul) quadrupole ion trap comprising a ring electrode and two end-cap electrodes, the ring electrode and the end-cap electrodes having a hyperbolic surface.
According to another embodiment the first ion trap comprises one or more cylindrical ring electrodes and two substantially planar end-cap electrodes.
According to another embodiment the first ion trap comprises one, two, three or more than three ring electrodes and two substantially planar end-cap electrodes.
One of the end-cap electrodes may comprise a sample or target plate. The sample or target plate may comprise a substrate with a plurality of sample regions arranged preferably in a microtitre format wherein, for example, the pitch spacing between samples is approximately or exactly 18 mm, 9 mm, 4.5 mm, 2.25 mm or 1.125 mm. Up to or at least 48, 96, 384, 1536 or 6144 samples may be arranged to be received on the sample or target plate. A laser beam or an electron beam is preferably targeted in use at the sample or target plate.
One of the end-cap electrodes of the first ion trap may comprise a mesh or grid.
The first ion trap may comprise a 2D (linear) quadrupole ion trap comprising a plurality of rod electrodes and two end electrodes.
According to other less preferred embodiments the first ion trap may comprise a segmented ring set comprising a plurality of electrodes having apertures through which ions are transmitted or a Penning ion trap.
A first AC or RF voltage having a first amplitude is preferably applied to the first ion trap. The first amplitude is preferably selected from the group consisting of: (i) 0-250 Vpp; (ii) 250-500 Vpp; (iii) 500-750 Vpp; (iv) 750-1000 Vpp; (v) 1000-1250 Vpp; (vi) 1250-1500 Vpp; (vii) 1500-1750 Vpp; (viii) 1750-2000 Vpp; (ix) 2000-2250 Vpp; (x) 2250-2500 Vpp; (xi) 2500-2750 Vpp; (xii) 2750-3000 Vpp; (xiii) 3000-3250 Vpp; (xiv) 3250-3500 Vpp; (xv) 3500-3750 Vpp; (xvi) 3750-4000 Vpp; (xvii) 4000-4250 Vpp; (xviii) 4250-4500 Vpp; (xix) 4500-4750 Vpp; (xx) 4750-5000 Vpp; (xxi) 5000-5250 Vpp; (xxii) 5250-5500 Vpp; (xxiii) 5500-5750 Vpp; (xxiv) 5750-6000 Vpp; (xxv) 6000-6250 Vpp; (xxvi) 6250-6500 Vpp; (xxvii) 6500-6750 Vpp: (xxviii) 6750-7000 Vpp; (xxix) 7000-7250 Vpp; (xxx) 7250-7500 Vpp; (xxxi) 7500-7750 Vpp; (xxxii) 7750-8000 Vpp; (xxxiii) 8000-8250 Vpp; (xxxiv) 8250-8500 Vpp; (xxxv) 8500-8750 Vpp; (xxxvi) 8750-9000 Vpp; (xxxvii) 9250-9500 Vpp; (xxxviii) 9500-9750 Vpp; (xxxix) 9750-10000 Vpp; and (xl)  greater than 10000 Vpp.
The first AC or RF voltage preferably has a frequency within a range selected from the group consisting of: (i)  less than 100 kHz; (ii) 100-200 kHz; (iii) 200-400 kHz; (iv) 400-600 kHz; (v) 600-800 kHz; (vi) 800-1000 kHz; (vii) 1.0-1.2 MHz; (viii) 1.2-1.4 MHz; (ix) 1.4-1.6 MHz; (x) 1.6-1.8 MHz; (xi) 1.8-2.0 MHz; and (xii)  greater than 2.0 MHz.
The second ion trap preferably comprises a quadrupole ion trap.
The second ion trap may comprise a 3D (Paul) quadrupole ion trap comprising a ring electrode and two end-cap electrodes, the ring electrode and the end-cap electrodes having a hyperbolic surface. Alternatively, the second ion trap may comprise a cylindrical ring electrode and two substantially planar end-cap electrodes.
The second ion trap may comprise one, two, three or more than three ring electrodes and two substantially planar end-cap electrodes. One or more of the end-cap electrodes of the second ion trap may comprise a mesh or grid.
According to another embodiment the second ion trap may comprise a 2D (linear) quadrupole ion trap comprising a plurality of rod electrodes and two end electrodes.
According to less preferred embodiments the second ion trap may comprise a segmented ring set comprising a plurality of electrodes having apertures through which ions are transmitted or a Penning ion trap.
A second AC or RF voltage having a second amplitude is preferably applied to the second ion trap. The second amplitude is preferably selected from the group consisting of: (i) 0-250 Vpp; (ii) 250-500 Vpp; (iii) 500-750 Vpp; (iv) 750-1000 Vpp; (v) 1000-1250 Vpp; (vi) 1250-1500 Vpp; (vii) 1500-1750 Vpp; (viii) 1750-2000 Vpp; (ix) 2000-2250 Vpp; (x) 2250-2500 Vpp; (xi) 2500-2750 Vpp; (xii) 2750-3000 Vpp; (xiii) 3000-3250 Vpp; (xiv) 3250-3500 Vpp; (xv) 3500-3750 Vpp; (xvi) 3750-4000 Vpp; (xvii) 4000-4250 Vpp; (xviii) 4250-4500 Vpp; (xix) 4500-4750 Vpp; (xx) 4750-5000 Vpp; (xxi) 5000-5250 Vpp; (xxii) 5250-5500 Vpp; (xxiii) 5500-5750 Vpp; (xxiv) 5750-6000 Vpp; (xxv) 6000-6250 Vpp; (xxvi) 6250-6500 Vpp; (xxvii) 6500-6750 Vpp; (xxviii) 6750-7000 Vpp; (xxix) 7000-7250 Vpp; (xxx) 7250-7500 Vpp; (xxxi) 7500-7750 Vpp; (xxxii) 7750-8000 Vpp; (xxxiii) 8000-8250 Vpp; (xxxiv) 8250-8500 Vpp; (xxxv) 8500-9750 Vpp; (xxxvi) 8750-9000 Vpp; (xxxvii) 9250-9500 Vpp; (xxxviii) 9500-9750 Vpp; (xxxix) 9750-10000 Vpp; and (xl)  greater than 10000 Vpp.
The second AC or RF voltage preferably has a frequency within a range selected from the group consisting of: (i)  less than 100 kHz; (ii) 100-200 kHz; (iii) 200-400 kHz; (iv) 400-600 kHz; (v) 600-800 kHz; (vi) 800-1000 kHz; (vii) 1.0-1.2 MHz; (viii) 1.2-1.4 MHz; (ix) 1.4-1.6 MHz; (x) 1.6-1.8 MHz; (xi) 1.8-2.0 MHz; and (xii)  greater than 2.0 MHz.
The amplitude of an AC or RF voltage applied to the first ion trap is preferably greater than the amplitude of an AC or RF voltage applied to the second ion trap.
The amplitude of an AC or RF voltage applied to the first ion trap is preferably greater than the amplitude of an AC or RF voltage applied to the second ion trap by at least x Vpp and wherein x is selected from the group consisting of: (i) 5; (ii) 10; (iii) 20; (iv) 30; (v) 40: (vi) 50; (vii) 60; (viii) 70; (ix) 80; (x) 90; (xi) 100; (xii) 110; (xiii) 120; (xiv) 130; (xv) 140; (xvi) 150; (xvii) 160; (xviii) 170; (xix) 180; (xx) 190; (xxi) 200; (xxii) 250; (xxiii) 300; (xxiv) 350; (xxv) 400; (xxvi) 450; (xxvii) 500; (xxviii) 550; (xxix) 600; (xxx) 650; (xxxi) 700; (xxxii) 750; (xxxiii) 800; (xxxiv) 850; (xxxv) 900; (xxxvi) 950; and (xxxvii) 1000.
The first ion trap and/or the second ion trap are preferably maintained at a pressure selected from the group consisting of; (i) greater than or equal to 0.0001 mbar; (ii) greater than or equal to 0.0005 mbar; (iii) greater than or equal to 0.001 mbar; (iv) greater than or equal to 0.005 mbar; (v) greater than or equal to 0.01 mbar; (vi) greater than or equal to 0.05 mbar; (vii) greater than or equal to 0.1 mbar; (viii) greater than or equal to 0.5 mbar: (ix) greater than or equal to 1 mbar; (x) greater than or equal to 5 mbar; and (xi) greater than or equal to 10 mbar.
The first ion trap and/or the second ion trap are preferably maintained at a pressure selected from the group consisting of: (i) less than or equal to 10 mbar; (ii) less than or equal to 5 mbar; (iii) less than or equal to 1 mbar; (iv) less than or equal to 0.5 mbar; (v) less than or equal to 0.1 mbar; (vi) less than or equal to 0.05 mbar; (vii) less than or equal to 0.01 mbar; (viii) less than or equal to 0.005 mbar; (ix) less than or equal to 0.001 mbar; (x) less than or equal to 0.0005 mbar; and (xi) less than or equal to 0.0001 mbar.
The first ion trap and/or the second ion trap are preferably maintained, in use, at a pressure selected from the group consisting of: (i) between 0.0001 and 10 mbar; (ii) between 0.0001 and 1 mbar; (iii) between 0.0001 and 0.1 mbar; (iv) between 0.0001 and 0.01 mbar; (v) between 0.0001 and 0.001 mbar; (vi) between 0.001 and 10 mbar; (vii) between 0.001 and 1 mbar; (viii) between 0.001 and 0.1 mbar; (ix) between 0.001 and 0.01 mbar; (x) between 0.01 and 10 mbar; (xi) between 0.01 and 1 mbar; (xii) between 0.01 and 0.1 mbar; (xiii) between 0.1 and 10 mbar; (xiv) between 0.1 and 1 mbar; and (xv) between 1 and 10 mbar.
According to other embodiments further ion traps may be provided in series with the first and second ion traps. Accordingly, a third ion trap may be provided and which is arranged to have, in use, a third low mass cut-off, the third low mass cut-off being lower than the second low mass cut-off so that at least some ions having mass to charge ratios lower than the first and second mass cut-offs which are not trapped in the first and second ion traps are trapped in the third ion trap.
A third AC or RF voltage having a third amplitude may be applied to the third ion trap. The third amplitude is preferably selected from the group consisting of: (i) 0-250 Vpp; (ii) 250-500 Vpp; (iii) 500-750 Vpp; (iv) 750-1000 Vpp; (v) 1000-1250 Vpp; (vi) 1250-1500 Vpp; (vii) 1500-1750 Vpp; (viii) 1750-2000 Vpp; (ix) 2000-2250 Vpp; (x) 2250-2500 Vpp; (xi) 2500-2750 Vpp; (xii) 2750-3000 Vpp; (xiii) 3000-3250 Vpp; (xiv) 3250-3500 Vpp; (xv) 3500-3750 Vpp; (xvi) 3750-4000 Vpp; (xvii) 4000-4250 Vpp; (xviii) 4250-4500 Vpp; (xix) 4500-4750 Vpp; (xx) 4750-5000 Vpp; (xxi) 5000-5250 Vpp; (xxii) 5250-5500 Vpp; (xxiii) 5500-5750 Vpp; (xxiv) 5750-6000 Vpp; (xxv) 6000-6250 Vpp; (xxvi) 6250-6500 Vpp; (xxvii) 6500-6750 Vpp; (xxviii) 6750-7000 Vpp; (xxix) 7000-7250 Vpp; (xxx) 7250-7500 Vpp; (xxxi) 7500-7750 Vpp; (xxxii) 7750-8000 Vpp; (xxxiii) 8000-8250 Vpp; (xxxiv) 8250-8500 Vpp; (xxxv) 8500-8750 Vpp; (xxxvi) 8750-9000 Vpp; (xxxvii) 9250-9500 Vpp; (xxxviii) 9500-9750 Vpp; (xxxix) 9750-10000 Vpp; and (xl)  greater than 10000 Vpp.
The third AC or RF voltage preferably has a frequency within a range selected from the group consisting of: (i)  less than 100 kHz; (ii) 100-200 kHz; (iii) 200-400 kHz; (iv) 400-600 kHz: (v) 600-800 kHz; (vi) 800-1000 kHz; (vii) 1.0-1.2 MHz; (viii) 1.2-1.4 MHz; (ix) 1.4-1.6 MHz; (x) 1.6-1.8 MHz; (xi) 1.8-2.0 MHz; and (xii)  greater than 2.0 MHz.
The amplitude of an AC or RF voltage applied to the second ion trap is preferably greater than the third amplitude.
A fourth ion trap may be provided and which is preferably arranged to have, in use, a fourth low mass cut-off, the fourth low mass cut-off being lower than the third low mass cut-off so that at least some ions having mass to charge ratios lower than the first, second and third mass cut-offs which are not trapped in the first, second and third ion traps are trapped in the fourth ion trap.
A fourth AC or RF voltage having a fourth amplitude is preferably applied to the fourth ion trap. The fourth amplitude is preferably selected from the group consisting of: (i) 0-250 Vpp; (ii) 250-500 Vpp; (iii) 500-750 Vpp; (iv) 750-1000 Vpp; (v) 1000-1250 Vpp; (vi) 1250-1500 Vpp; (vii) 1500-1750 Vpp; (viii) 1750-2000 Vpp; (ix) 2000-2250 Vpp; (x) 2250-2500 Vpp; (xi) 2500-2750 Vpp; (xii) 2750-3000 Vpp; (xiii) 3000-3250 Vpp; (xiv) 3250-3500 Vpp; (xv) 3500-3750 Vpp; (xvi) 3750-4000 Vpp; (xvii) 4000-4250 Vpp: (xviii) 4250-4500 Vpp; (xix) 4500-4750 Vpp; (xx) 4750-5000 Vpp; (xxi) 5000-5250 Vpp; (xxii) 5250-5500 Vpp; (xxiii) 5500-5750 Vpp; (xxiv) 5750-6000 Vpp; (xxv) 6000-6250 Vpp; (xxvi) 6250-6500 Vpp; (xxvii) 6500-6750 Vpp; (xxviii) 6750-7000 Vpp; (xxix) 7000-7250 Vpp; (xxx) 7250-7500 Vpp; (xxxi) 7500-7750 Vpp; (xxxii) 7750-8000 Vpp; (xxxiii) 8000-8250 Vpp; (xxxiv) 8250-8500 Vpp; (xxxv) 8500-8750 Vpp; (xxxvi) 8750-9000 Vpp; (xxxvii) 9250-9500 Vpp; (xxxviii) 9500-9750 Vpp; (xxxix) 9750-10000 Vpp; and (xl)  greater than 10000 Vpp.
The fourth AC or RF voltage preferably has a frequency within a range selected from the group consisting of: (i)  less than 100 kHz; (ii) 100-200 kHz; (iii) 200-400 kHz: (iv) 400-600 kHz; (v) 600-800 kHz: (vi) 800-1000 kHz; (vii) 1.0-1.2 MHz; (viii) 1.2-1.4 MHz; (ix) 1.4-1.6 MHz; (x) 1.6-1.8 MHz; (xi) 1.8-2.0 MHz; and (xii)  greater than 2.0 MHz.
The third amplitude is preferably greater than the fourth amplitude.
According to other embodiments five, six, seven, eight, nine, ten or more than ten ion traps may be provided in series.
A continuous or pulsed ion source is preferably provided. The ion source may comprise an Electrospray ion source, an Atmospheric Pressure Chemical Ionisation (xe2x80x9cAPCIxe2x80x9d) ion source, an Atmospheric Pressure MALDI ion source, an Electron Ionisation (xe2x80x9cEIxe2x80x9d) ion source, a Chemical Ionisation (xe2x80x9cCIxe2x80x9d) ion source, a Field Desorption Ionisation (xe2x80x9cFIxe2x80x9d) ion source, a Matrix Assisted Laser Desorption Ionisation (xe2x80x9cMALDIxe2x80x9d) ion source, a Laser Desorption Ionisation (xe2x80x9cLDIxe2x80x9d) ion source, a Laser Desorption/Ionisation on Silicon (xe2x80x9cDIOSxe2x80x9d) ion source, a Surface Enhanced Laser Desorption Ionisation (xe2x80x9cSELDIxe2x80x9d) ion source or a Fast Atom Bombardment (xe2x80x9cFABxe2x80x9d) ion source.
An ion detector may be arranged downstream of the second ion trap. The ion detector may comprise an electron multiplier, a photo-multiplier or a channeltron.
A Time of Flight mass analyser, such as an axial Time of Flight mass analyser or more preferably an orthogonal acceleration Time of Flight mass analyser may be provided.
In addition to the first, second and optionally third, fourth etc. ion traps, a further ion trap is preferably provided. The further ion trap preferably comprises a quadrupole ion trap.
The further ion trap may comprise a 3D (Paul) quadrupole ion trap comprising a ring electrode and two end-cap electrodes, the ring electrode and the end-cap electrodes having a hyperbolic surface.
The further ion trap may comprise one or more cylindrical ring electrodes and two substantially planar end-cap electrodes.
Alternatively, the further ion trap may comprise one, two, three or more than three ring electrodes and two substantially planar end-cap electrodes.
According to an embodiment one or more of the end-cap electrodes of the further ion trap may comprise a mesh or grid.
According to another embodiment the further ion trap may comprise a 2D (linear) quadrupole ion trap comprising a plurality of rod electrodes and two end electrodes.
According to less preferred embodiments the further ion trap may comprise a segmented ring set comprising a plurality of electrodes having apertures through which ions are transmitted or a Penning ion trap.
Ions are preferably pulsed out of the further ion trap in a non mass-selective mode or non scanning mode. For example, ions may be pulsed out of the further ion trap by applying a DC voltage extraction pulse to the end-cap electrodes of the further ion trap. A DC voltage may also or alternatively be applied to the ring electrode(s) of the further ion trap so that a more linear axial DC electric field gradient is provided.
Additional ion traps may be provided for storing parent ions in MS/MS modes of operation. The mass spectrometer may therefore further comprise a first additional ion trap. The first additional ion trap preferably comprises a quadrupole ion trap. The first additional ion trap may comprise a 3D (Paul) quadrupole ion trap comprising a ring electrode and two end-cap electrodes, the ring electrode and the end-cap electrodes having a hyperbolic surface.
Alternatively, the first additional ion trap may comprise one or more cylindrical ring electrodes and two substantially planar end-cap electrodes.
The first additional ion trap may comprise one, two, three or more than three ring electrodes and two substantially planar end-cap electrodes. One or more end-cap electrodes of the first additional ion trap may comprise a mesh or grid.
The first additional ion trap may comprise a 2D (linear) quadrupole ion trap comprising a plurality of rod electrodes and two end electrodes. Alternatively, the first additional ion trap may comprise a segmented ring set comprising a plurality of electrodes having apertures through which ions are transmitted or a Penning ion trap.
A second additional ion trap for storing parent ions in MS/MS modes of operation may preferably be provided. The second additional ion trap may comprise a quadrupole ion trap. The second additional ion trap may comprise a 3D (Paul) quadrupole ion-trap comprising a ring electrode and two end-cap electrodes, the ring electrode and the end-cap electrodes having a hyperbolic surface.
The second additional ion trap may comprise one or more cylindrical ring electrodes and two substantially planar end-cap electrodes. Alternatively, the second additional ion trap may comprise one, two, three or more than three ring electrodes and two substantially planar end-cap electrodes. One or more end-cap electrode of the second additional ion trap may comprise a mesh or grid.
The second additional ion trap may comprise a 2D (linear) quadrupole ion trap comprising a plurality of rod electrodes and two end electrodes. Alternatively, the second additional ion trap may comprise a segmented ring set comprising a plurality of electrodes having apertures through which ions are transmitted or a Penning ion trap.
According to another aspect of the present invention, there is provided a method of mass spectrometry, comprising:
providing a first ion trap having a first low mass cut-off;
providing a second ion trap having a second low mass cut-off, the second low mass cut-off being lower than the first low mass cut-off;
trapping some ions in the first ion trap; and
trapping in the second ion trap at least some ions having mass to charge ratios lower than the first low mass cut-off which are not trapped in the first ion trap.
In the various embodiments contemplated in the present application when a quadrupole ion trap is used with multiple inner (or ring) electrodes (which are simpler to manufacture than electrodes having an hyperbolic surface) the quadrupole field may be generated by applying different AC or RF voltage amplitudes of the same phase to each inner electrode. The inner electrodes should preferably be symmetrical about the centre of the ion trap. However, by selecting a certain aperture or inner radius for the ring electrodes it is possible to generate an AC or RF electric field which is close to quadrupolar with the same amplitude and phase of AC or RF applied to each ring electrode and with the opposing phase applied to the end-cap electrodes.
If an ion trap with e.g. flat or thin cylindrical electrodes has to pulse ions out of the ion trap (for example, to pulse the ions into an axial or orthogonal acceleration Time of Flight mass analyser) then the DC voltages applied to the electrodes in such an ion extraction mode can be arranged so that a substantially linear electric field is generated. This may be advantageous in terms of ion transfer efficiency. Also, there may be some degree of time of flight spatial focusing after pulsed extraction.
According to another aspect of the present invention there is provided a mass spectrometer comprising:
a quadrupole ion trap;
a further ion trap arranged to receive ions ejected from the quadrupole ion trap; and
a Time of Flight mass analyser arranged to receive ions ejected from the further ion trap;
wherein in a first mode of operation the further ion trap receives a pulse of ions which have been mass-selectively ejected from or scanned out of the quadrupole ion trap, wherein the ratio of the maximum mass to charge ratio of ions in the pulse of ions to the minimum mass to charge ratio of ions in the pulse of ions is a maximum of x, and wherein xxe2x89xa64.0, and wherein the ions received from the quadrupole ion trap are collisionally cooled within the further ion trap.
Preferably, x is selected from the group consisting of: (i) 3.9; (ii) 3.8; (iii) 3.7; (iv) 3.6; (v) 3.5; (vi) 3.4; (vii) 3.3; (viii) 3.2; (ix) 3.1; (x) 3.0; (xi) 2.9; (xii) 2.8; (xiii) 2.7; (xiv) 2.6; (xv) 2.5; (xvi) 2.4; (xvii) 2.3; (xviii) 2.2; (xix) 2.1; (xx) 2.0; (xxi) 1.9; (xxii) 1.8; (xxiii) 1.7; (xxiv) 1.6; (xxv) 1.5; (xxvi) 1.4; (xxvii) 1.3; (xxviii) 1.2; and (xxix) 1.1.
In a first mode of operation the further ion trap is preferably maintained at a pressure selected from the group consisting of: (i) greater than or equal to 0.0001 mbar; (ii) greater than or equal to 0.0005 mbar; (iii) greater than or equal to 0.001 mbar; (iv) greater than or equal to 0.005 mbar; (v) greater than or equal to 0.01 mbar; (vi) greater than or equal to 0.05 mbar; (vii) greater than or equal to 0.1 mbar; (viii) greater than or equal to 0.5 mbar; (ix) greater than or equal to 1 mbar; (x) greater than or equal to 5 mbar; and (xi) greater than or equal to 10 mbar.
In a first mode of operation the further ion trap is preferably maintained at a pressure selected from the group consisting of: (i) less than or equal to 10 mbar; (ii) less than or equal to 5 mbar; (iii) less than or equal to 1 mbar; (iv) less than or equal to 0.5 mbar; (v) less than or equal to 0.1 mbar; (vi) less than or equal to 0.05 mbar; (vii) less than or equal to 0.01 mbar; (viii) less than or equal to 0.005 mbar; (ix) less than or equal to 0.001 mbar; (x) less than or equal to 0.0005 mbar; and (xi) less than or equal to 0.0001 mbar.
In a first mode of operation the further ion trap is preferably maintained at a pressure selected from the group consisting of: (i) between 0.0001 and 10 mbar; (ii) between 0.0001 and 1 mbar; (iii) between 0.0001 and 0.1 mbar; (iv) between 0.0001 and 0.01 mbar; (v) between 0.0001 and 0.001 mbar; (vi) between 0.001 and 10 mbar; (vii) between 0.001 and 1 mbar; (viii) between 0.001 and 0.1 mbar; (ix) between 0.001 and 0.01 mbar; (x) between 0.01 and 10 mbar; (xi) between 0.01 and 1 mbar; (xii) between 0.01 and 0.1 mbar; (xiii) between 0.1 and 10 mbar; (xiv) between 0.1 and 1 mbar; and (xv) between 1 and 10 mbar.
In a second mode of operation ions are preferably pulsed out of or ejected from the further ion trap in a non mass-selective or a non-scanning manner i.e. ions are not resonantly excited out of the further ion trap and hence the ions are not ejected from the further ion trap in a substantially excited state. In the second mode of operation ions may be pulsed out of or ejected from the further ion trap by applying one or more DC voltage extraction pulses to the further ion trap. The one or more DC extraction voltages may also be applied to one or more end or end-cap electrodes of the further ion trap and/or to one or more central or ring electrodes of the further ion trap. Preferably, in the second mode of operation AC or RF voltages are not substantially applied to the electrodes of the further ion trap.
In the second mode of operation the further ion trap is preferably maintained at a lower pressure than when the further ion trap is operated in the first mode of operation. The further ion trap is preferably maintained at a pressure selected from the following group when operated in the second mode of operation: (i)  less than 5xc3x9710xe2x88x922 mbar; (ii)  less than 10xe2x88x922 mbar; (iii)  less than 5xc3x9710xe2x88x923 mbar; (iv)  less than 10xe2x88x923 mbar; (v)  less than 5xc3x9710xe2x88x924 mbar; (vi)  less than 10xe2x88x924 mbar; (vii)  less than 5xc3x9710xe2x88x925 mbar; (viii)  less than 10xe2x88x925 mbar; (ix)  less than 5xc3x9710xe2x88x926 mbar; and (x)  less than 10xe2x88x926 mbar.
In the first mode of operation a pulse of ions ejected from the quadrupole ion trap and received by the further ion trap preferably has a first range of energies xcex94E1 and wherein in the second mode of operation ions ejected from the further ion trap preferably have a second range of energies xcex94E2, wherein xcex94E2 less than xcex94E1. xcex94E1/xcex94E2 is preferably at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100. xcex94E1 is preferably at least 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 eV and xcex94E2 is preferably a maximum of 1, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02 or 0.01 eV.
According to another aspect of the present invention there is provided a method of mass spectrometry, comprising:
providing a quadrupole ion trap, a further ion trap arranged to receive ions ejected from the quadrupole ion trap and a Time of Flight mass analyser arranged to receive ions ejected from the further ion trap;
mass-selectively ejecting from or scanning out of the quadrupole ion trap a pulse of ions in a first mode of operation wherein the further ion trap receives the pulse of ions and wherein the ratio of the maximum mass to charge ratio of ions in the pulse of ions to the minimum mass to charge ratio of ions in the pulse of ions is a maximum of x, and wherein xxe2x89xa64.0; and
collisionally cooling the ions received from the quadrupole ion trap within the further ion trap.
According to another aspect of the present invention there is provided a method of mass spectrometry comprising:
storing parent ions having a first mass to charge ratio in a first ion trap;
storing at least some other parent ions having mass to charge ratios other than the first mass to charge ratio in one or more additional ion traps;
fragmenting the parent ions having the first mass to charge ratio in the first ion trap so as to form fragment ions;
trapping some of the fragment ions in the first ion trap having a first low mass cut-off; and
trapping other of the fragment ions in a second ion trap having a second low mass cut-off, wherein the second low mass cut-off is lower than the first low mass cut-off.
According to another aspect of the present invention, there is provided a method of mass spectrometry comprising:
storing parent ions having a first mass to charge ratio in an ion trap;
storing at least some other parent ions having mass to charge ratios other than the first mass to charge ratio in one or more additional ion traps;
fragmenting the parent ions having the first mass to charge ratio in a first ion trap so as to form fragment ions;
trapping some of the fragment ions in the first ion trap having a first low mass cut-off; and
trapping other of the fragment ions in a second ion trap having a second low mass cut-off, wherein the second low mass cut-off is lower than the first low mass cut-off.
According to another aspect of the present invention, there is provided a method of mass spectrometry comprising:
storing parent ions having a first mass to charge ratio in an ion trap;
storing at least some other parent ions having mass to charge ratios other than the first mass to charge ratio in one or more additional ion traps;
fragmenting the parent ions having the first mass to charge ratio so as to form fragment ions;
trapping some of the fragment ions in a first ion trap having a first low mass cut-off; and
trapping other of the fragment ions in a second ion trap having a second low mass cut-off, wherein the second low mass cut-off is lower than the first low mass cut-off.
The ion trap may be the same as the first ion trap.
Fragment ions are preferably collisionally cooled within the first and/or second ion traps. Some fragment ions are preferably scanned out of or mass-selectively ejected out of the first and/or second ion traps whilst retaining other fragment ions within the first and/or second ion traps.
In a first mode of operation at least some fragment ions which have been scanned out of or mass-selectively ejected from either the first ion trap and/or the second ion trap may be received, trapped and collisionally cooled in a further ion trap.
A pulse of ions ejected from or pulsed out of the further ion trap in a second mode of operation is preferably received by a Time of Flight mass analyser e.g. an axial or orthogonal acceleration Time of Flight mass analyser.
According to another aspect of the present invention, there is provided a mass spectrometer comprising:
a first ion trap wherein in use parent ions having a first mass to charge ratio are stored therein;
one or more additional ion traps wherein in use at least some other parent ions having mass to charge ratios other than the first mass to charge ratio are stored therein; and
a second ion trap;
wherein in use the parent ions having the first mass to charge ratio are fragmented in the first ion trap so as to form fragment ions and wherein some of the fragment ions are trapped in the first ion trap having a first low mass cut-off and other of the fragment ions are trapped in the second ion trap having a second low mass cut-off, wherein the second low mass cut-off is lower than the first low mass cut-off.
According to another aspect of the present invention there is provided a mass spectrometer comprising:
an ion trap wherein in use parent ions having a first mass to charge ratio are stored therein;
one or more additional ion traps wherein in use at least some other parent ions having mass to charge ratios other than the first mass to charge ratio are stored therein;
a first ion trap; and
a second ion trap;
wherein in use the parent ions having the first mass to charge ratio are fragmented in the first ion trap so as to form fragment ions and wherein some of the fragment ions are trapped in the first ion trap having a first low mass cut-off and other of the fragment ions are trapped in a second ion trap having a second low mass cut-off, wherein the second low mass cut-off is lower than the first low mass cut-off.
According to another aspect of the present invention there is provided a mass spectrometer comprising:
an ion trap wherein in use parent ions having a first mass to charge ratio are stored therein;
one or more additional ion traps wherein in use at least some other parent ions having mass to charge ratios other than the first mass to charge ratio are stored therein;
a first ion trap; and
a second ion trap;
wherein in use the parent ions having the first mass to charge ratio are fragmented so as to form fragment ions and wherein some of the fragment ions are trapped in the first ion trap having a first low mass cut-off and wherein other of the fragment ions are trapped in a second ion trap having a second low mass cut-off, wherein the second low mass cut-off is lower than the first low mass cut-off.
According to another aspect of the present invention there is provided a mass spectrometer comprising:
a first ion trap, the first ion trap comprising an ion trap ion source comprising one or more central electrodes, a first end-cap electrode and a second end-cap electrode;
wherein a sample or target plate forms at least part of the first end-cap electrode of the first ion trap.
The ion trap ion source may comprise a Matrix Assisted Laser Desorption Ionisation (xe2x80x9cMALDIxe2x80x9d) ion trap ion source, a Laser Desorption Ionisation (xe2x80x9cLDIxe2x80x9d) ion trap ion source, a Laser Desorption/Ionization on Silicon (xe2x80x9cDIOSxe2x80x9d) ion trap ion source, a Surface Enhanced Laser Desorption Ionisation (xe2x80x9cSELDIxe2x80x9d) ion trap ion source or a Fast Atom Bombardment (xe2x80x9cFABxe2x80x9d) ion trap ion source.
According to another aspect of the present invention there is provided a method of mass spectrometry comprising:
providing a first ion trap, the first ion trap comprising an ion trap ion source comprising one or more central electrodes, a first end-cap electrode and a second end-cap electrode wherein a sample or target plate forms at least part of the first end-cap electrode;
arranging for a laser beam or an electron beam to impinge upon the sample or target plate; and
ionising samples or targets on the sample or target plate.